1. Field of the Invention
The present invention relates to a cleaning device used in manufacturing processes for various electronic devices manufactured on a disk-shaped wafer, such as semiconductor devices. More particularly, the present invention relates to a method and device for cleaning the edge portion and back face of a wafer while rotating the wafer.
2. Description of the Related Art
In the photolithography process of the semiconductor device fabrication processes, a resist coating process for coating a semiconductor wafer with a resist film is performed.
In general, the resist coating process is performed by using a spin-coating method. In the procedure of the spin-coating method, resist solution is dispensed to the center of a spinning wafer and spread across the surface of the wafer by centrifugal force. The spin speed of the semiconductor wafer is controlled, whereby the thickness of a layer of resist solution on the semiconductor wafer is controlled. In this process, the resist solution sometimes overflows the target bounds within which a resist film is to be formed, and adheres to the edge portion and even to the back face of the semiconductor wafer. Japanese Patent Application Unexamined Publication No. H02-198131 describes a cleaning process in which, to remove resist solution adhering to the edge portion and back face of a semiconductor wafer, for example, cleaning liquid is supplied to the back face of the semiconductor wafer while rotating the semiconductor wafer, thus cleaning the edge portion and back face of the semiconductor wafer. After the cleaning process is complete, a process for drying the semiconductor wafer is performed in which the semiconductor wafer is further continuously rotated, thereby spinning off the cleaning liquid adhering to the back face of the semiconductor wafer. In this manner, the resist coating process is complete, and a resist film with a predetermined thickness is formed on the semiconductor wafer.
Moreover, during a lot process in the semiconductor fabrication processes, there are some cases where dust generated from semiconductor wafers or from processing equipment adheres to a semiconductor wafer. Of the generated dust particulates, those adhering to the edge portion and back face of the semiconductor wafer are removed, similarly to the removal of resist, by supplying cleaning liquid from the back side of the semiconductor wafer while rotating the semiconductor wafer.
However, different semiconductor wafers have different edge shapes, which also vary with the manufacture. Accordingly, there are some cases where dust or resist adhering to the edge portion of a semiconductor wafer cannot be perfectly removed and consequently remains. If resist remains on the edge portion of a semiconductor wafer, a problem arises that resist particles may be generated due to contact with a robot arm and the like when the semiconductor wafer is being transported. If dust remains on the edge portion of a semiconductor wafer, a problem arises that the dust may migrate to a device region on the front face of the semiconductor wafer, resulting in a fatal defect, leading to a decrease in yield. On the other hand, if a large quantity of cleaning liquid is supplied to remove resist and dust remaining on the edge portion, a problem also arises that the cleaning liquid may migrate to the front side and enter a device region on the front face of the semiconductor wafer to reduce the resist-coated region formed in the device region, resulting in a smaller device region.
These problems are not peculiar to the semiconductor device fabrication, and similar problems also exist in the manufacturing of various electronic devices such as crystal liquid displays, magnetic storage media, and superconducting devices.